Feat[bmq]: Add interfaces in DTTracer to serialize and deserialize span

src/groups/bmq/bmqimp/bmqimp_brokersession.t.cpp

@@ -2798,6 +2798,12 @@ class DTTestSpan : public bmqpi::DTSpan {
     {
         return d_operation;
     }
+
+    int finish() const BSLS_KEYWORD_OVERRIDE
+    {
+        // NOT IMPLEMENTED
+        return 0;
+    }
 };
 
 class DTTestTracer : public bmqpi::DTTracer {
@@ -2834,6 +2840,26 @@ class DTTestTracer : public bmqpi::DTTracer {
             d_allocator_p);
         return result;
     }
+
+    int
+    serializeSpan(BSLS_ANNOTATION_UNUSED bsl::vector<unsigned char>* buffer,
+                  BSLS_ANNOTATION_UNUSED const bsl::shared_ptr<bmqpi::DTSpan>&
+                      dtSpan) const BSLS_KEYWORD_OVERRIDE
+    {
+        // NOT IMPLEMENTED
+        return 0;
+    }
+
+    int deserializeAndCreateChildSpan(
+        BSLS_ANNOTATION_UNUSED bsl::shared_ptr<bmqpi::DTSpan>* child,
+        BSLS_ANNOTATION_UNUSED const bsl::vector<unsigned char>& buffer,
+        BSLS_ANNOTATION_UNUSED const bsl::string_view& operation,
+        BSLS_ANNOTATION_UNUSED const bmqpi::DTSpan::Baggage& baggage) const
+        BSLS_KEYWORD_OVERRIDE
+    {
+        // NOT IMPLEMENTED
+        return 0;
+    }
 };
 
 }  // close unnamed namespace

src/groups/bmq/bmqpi/bmqpi_dtspan.h

@@ -49,13 +49,21 @@ class DTSpan {
     // PUBLIC CREATORS
 
     /// Destructor
+    /// Upon destruction, `finish()` will be called to mark the end of a span.
     virtual ~DTSpan();
 
     // PUBLIC ACCESSORS
 
     /// Returns the name of the operation that this `DTSpan` represents.
     virtual bsl::string_view operation() const = 0;
 
+    /// Mark the end of the `DTSpan`. Only the timing of the first call for a
+    /// given `DTSpan` will be recorded, and implementations are free to ignore
+    /// all further calls.  A finished Span can not be re-started. If finish()
+    /// is not directly called, it will be called from the destructor.
+    /// Return 0 on success, or a non-zero error code on error.
+    virtual int finish() const = 0;
+
     // =============
     // class Baggage
     // =============

src/groups/bmq/bmqpi/bmqpi_dtspan.t.cpp

@@ -29,6 +29,7 @@ using namespace BloombergLP;
 /// A test implementation of the `bmqpi::DTSpan` protocol.
 struct DTSpanTestImp : public bsls::ProtocolTestImp<bmqpi::DTSpan> {
     bsl::string_view operation() const BSLS_KEYWORD_OVERRIDE;
+    int              finish() const BSLS_KEYWORD_OVERRIDE;
 };
 
 // Define one of DTSpanTestImp methods out-of-line, to instruct the compiler to
@@ -38,6 +39,11 @@ bsl::string_view DTSpanTestImp::operation() const
     return markDone();
 }
 
+int DTSpanTestImp::finish() const
+{
+    return markDone();
+};
+
 // ============================================================================
 //                                    TESTS
 // ============================================================================

src/groups/bmq/bmqpi/bmqpi_dttracer.h

@@ -32,6 +32,7 @@
 // BDE
 #include <bsl_memory.h>
 #include <bsl_string_view.h>
+#include <bsl_vector.h>
 
 namespace BloombergLP {
 namespace bmqpi {
@@ -56,6 +57,22 @@ class DTTracer {
         const bsl::shared_ptr<DTSpan>& parent,
         const bsl::string_view&        operation,
         const DTSpan::Baggage&         baggage = DTSpan::Baggage()) const = 0;
+
+    /// Serialize the specified `dtSpan` into the specified `buffer`.
+    /// Return 0 on success, or a non-zero error code on error with `buffer`
+    /// being valid-but-unspecified.
+    virtual int serializeSpan(bsl::vector<unsigned char>*    buffer,
+                              const bsl::shared_ptr<DTSpan>& dtSpan) const = 0;
+
+    /// Deserialize the specified `buffer` as a span, and then construct a
+    /// new `DTSpan` in `child`, representing `operation` as a child of the
+    /// deserialized span and having the key-value tags defined by `baggage`.
+    /// Return 0 on success, or a non-zero error code on error.
+    virtual int deserializeAndCreateChildSpan(
+        bsl::shared_ptr<DTSpan>*          child,
+        const bsl::vector<unsigned char>& buffer,
+        const bsl::string_view&           operation,
+        const DTSpan::Baggage& baggage = DTSpan::Baggage()) const = 0;
 };
 
 }  // close package namespace

src/groups/bmq/bmqpi/bmqpi_dttracer.t.cpp

@@ -31,10 +31,21 @@ using namespace BloombergLP;
 
 /// A test implementation of the `bmqpi::DTTracer` protocol.
 struct DTTracerTestImp : public bsls::ProtocolTestImp<bmqpi::DTTracer> {
-    virtual bsl::shared_ptr<bmqpi::DTSpan> createChildSpan(
+    bsl::shared_ptr<bmqpi::DTSpan> createChildSpan(
         const bsl::shared_ptr<bmqpi::DTSpan>& parent,
         const bsl::string_view&               operation,
         const bmqpi::DTSpan::Baggage& baggage) const BSLS_KEYWORD_OVERRIDE;
+
+    int serializeSpan(bsl::vector<unsigned char>*           buffer,
+                      const bsl::shared_ptr<bmqpi::DTSpan>& dtSpan) const
+        BSLS_KEYWORD_OVERRIDE;
+
+    int deserializeAndCreateChildSpan(
+        bsl::shared_ptr<bmqpi::DTSpan>*   child,
+        const bsl::vector<unsigned char>& buffer,
+        const bsl::string_view&           operation,
+        const bmqpi::DTSpan::Baggage& baggage = bmqpi::DTSpan::Baggage()) const
+        BSLS_KEYWORD_OVERRIDE;
 };
 
 // Define one of DTTracerTestImp methods out-of-line, to instruct the
@@ -47,6 +58,21 @@ DTTracerTestImp::createChildSpan(const bsl::shared_ptr<bmqpi::DTSpan>&,
     return markDone();
 }
 
+int DTTracerTestImp::serializeSpan(bsl::vector<unsigned char>*,
+                                   const bsl::shared_ptr<bmqpi::DTSpan>&) const
+{
+    return markDone();
+}
+
+int DTTracerTestImp::deserializeAndCreateChildSpan(
+    bsl::shared_ptr<bmqpi::DTSpan>*,
+    const bsl::vector<unsigned char>&,
+    const bsl::string_view&,
+    const bmqpi::DTSpan::Baggage&) const
+{
+    return markDone();
+}
+
 // ============================================================================
 //                                    TESTS
 // ============================================================================
@@ -100,8 +126,13 @@ static void test1_breathingTest()
     BMQTST_ASSERT(tracer.testVirtualDestructor());
 
     PV("Verify that all methods are public and virtual");
-    bmqpi::DTSpan::Baggage empty;
+    bmqpi::DTSpan::Baggage     empty(bmqtst::TestHelperUtil::allocator());
+    bsl::vector<unsigned char> emptyVec(bmqtst::TestHelperUtil::allocator());
     BSLS_PROTOCOLTEST_ASSERT(tracer, createChildSpan(NULL, "", empty));
+    BSLS_PROTOCOLTEST_ASSERT(tracer, serializeSpan(NULL, NULL));
+    BSLS_PROTOCOLTEST_ASSERT(
+        tracer,
+        deserializeAndCreateChildSpan(NULL, emptyVec, "", empty));
 }
 
 // ============================================================================